Level controller and liquid remover for a refrigeration system

ABSTRACT

An apparatus in a refrigeration circuit for removing liquid entrained in refrigerant vapor on the suction side of the compressor and for controlling the level of refrigerant in the evaporator. The apparatus includes a chamber for holding liquid refrigerant at its lower portion, and for containing refrigerant vapors above the liquid for discharge to the compressor. The level of liquid refrigerant in the chamber is maintained at the level of liquid refrigerant in the evaporator, and a valve in the refrigerant line from the condenser to the evaporator is regulated according to the liquid refrigerant level in the apparatus to maintain a predetermined refrigerant level in the evaporator.

United States Patent Lesczynski [451 Aug. 13, 1974 [75] Inventor: Michael Lesczynski, Chittenango,

[73] Assignee: Carrier Corporation, Syracuse, NY.

[22] Filed: May 1, 1973 211 App]. No.: 356,277

[52] US. Cl. 62/160, 62/220 Heinrich 62/219 Phillips 62/219 Primary Examiner-Meyer Perlin Attorney, Agent, or Firm-J. Raymond Curtin; D. Peter Hochberg [57] ABSTRACT An apparatus in a refrigeration circuit for removing liquid entrained in refrigerant vapor on the suction side of the compressor and for controlling the level of refrigerant in the evaporator. The apparatus includes a chamber for holding liquid refrigerant at its lower portion, and for containing refrigerant vapors above the liquid for discharge to the compressor. The level of liquid refrigerant in the chamber is maintained at the level of liquid refrigerant in the evaporator, and a valve in the refrigerant line from the condenser to the evaporator is regulated according to the liquid refrigerant level in the apparatus to maintain a predetermined refrigerant level in the evaporator.

3 Claims, 2 Drawing Figures McGovern 62/219 PAIemwwm 3.828.567

' sum 1 or 2 FIG I PAIENTEUAUBI3'IBT4 3.828.567

SHEET 2 UF 2 FIG. 2

LEVEL CONTROLLER AND LIQUID REMOVER FOR AREFRIGERATION SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to means for removing liquid entrained in refrigerant fed to the compressorof a refrigeration system, and to means for controlling the level of refrigerant in the evaporator of the system. The present invention can be used to achieve such refrigerant control in reversible refrigeration circuits used in freeze-thaw sludge treatment systems.

2. Description of the Prior Art A system for concentrating sludge is disclosed in commonly assigned, copending US. Ser. No. 35 6, 276 filed in the name of Raineri et al. on even date herewith. The invention disclosed therein includes a reversible refrigeration circuit including a pair of heat exchangers which serve alternate andopposite functions as evaporatorsand as condensers, a compressor, and various refrigerant lines and valves. A sludge network operatively associated with the refrigeration circuit circulates raw sludge through the heat exchanger serving as the evaporator to freeze the raw sludge therein, while sludge previously frozen in the other heat exchanger (which is now serving as a condenser) melts. The movement of sludge through the system and the flow of refrigerant in the refrigeration circuit are controlled in a manner rendering the system efficient and economical.

In refrigeration circuits of the foregoing type, it is important to prevent liquid from entering the compressor in order to protect the compressor against damage. In addition, when the evaporator (which is alternately one heat exchanger and then the other) is of the flooded type, it is desirable to maintain a high liquid refrigerant level therein to maximize the heat absorbing ability of the refrigerant in the evaporator. In prior art systems, separate devices were used for removing liquid from the gas stream on the suction side of the compressor, and for regulating the level of refrigerant in the evaporator.

SUMMARY OF THE INVENTION An object of the present invention is to remove refrigerant liquid from the refrigerant vapor stream on the suction side of a compressor, and to regulate the refrigerant level in the evaporator of a refrigeration circuit.

Another object of the invention is to provide an apparatus of the foregoing type which is efficient, economical and effective.

Other objects will be apparent from the description to follow and from the appended claims.

The preceding objects are achieved according to a preferred embodiment of the invention by the provision of a device referred to herein as a level controlling suction knockout pot, which is installed inthe suction line of the compressor of a refrigeration circuit. A system in which employment of such a knockout pot is contemplated includes a pair of heat exchangers which serve alternate and opposite functions as evaporators and as condensers. The knockout pot operates both to remove liquid refrigerant entrained in the refrigerant gas stream being fed from the evaporator to the compressor and operates to maintain a predeterminedlevel of liquid refrigerant in the evaporator. When the refrigeration circuit is reversible, the knockout pot is appropriately connected .to both heat exchangers so that it will serve its function with regard to the evaporator regardless of which heat exchanger is acting in that capacity.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic drawing of a sludge treating system which incorporates a level controlling suction knockout pot according to the invention.

FIG. 2 shows a cutaway view of the level controlling suction knockout pot.

DESCRIPTION OF THE PREFERRED EMBODIMENT The level controlling suction knockout pot, or simply knockout pot, described herein finds particular utility 'in a sludge treating system of the type depicted in FIG.

1. This systemcomprises a reversible refrigeration circuit and an associated and cooperating sludge handling network. The refrigeration circuit has a pair of heat exchangers which are preferably falling film heat exchangers of the type disclosed in commonly assigned Ser. No. 231,274, now US. Pat. No. 3,745,782 which was filed on Mar. 2, 1972, in the name of Neyhart et al. and entitled Sludge Separation Systems. The refrigeration circuit includes a compressor and a pair of heat exchangers. Sludge moves through appropriate paths to be frozen and then thawed in the heat exchangers, and is discharged to a melted sludge tank for eventual discharge to settling tanks. One heat exchanger functions as an evaporator while the other heat exchanger functions as a condenser. Each time the direction of refrigerant flow reverses, the functions of the two heat exchangers reverse accordingly. During each phase of the refrigeration cycle, there is a period in which the compressor does not run but the refrigerant circulates nonetheless by virtue of a pressure differential therein. This is described in more detail in commonly assigned Ser. No. 356,235, filed on even date herewith in the name of .IamesS. Styron. Tanks for re ceiving raw sludge and melted sludge are disposed beneath the two heat exchangers, and pivotal dampers located beneath the heat exchangers direct raw sludge and melted sludge discharged by the two exchangers to the appropriate tanks. The flow of raw sludge into the system, the circulation of sludge through the heat exchangers, and the transfer of melted sludge out of the system are controlled by electrically operated valves and pumps in coordination with the refrigerant valves and pumps.

Referring now to FIG. 1, a sludge treatment system is shown which includes a closed refrigerant circuit and a sludge for receiving raw sludge discharged by either of the exchangers, a melted sludge tank refrigeration circuit includes a pair of identical heat exchangers 2 and 4, a knockout pot 6 which is described below in detail, a compressor 8 and an associated oil separator 10, a refrigerant receiver 11 (with a level glass 12), a set of lines for conducting refrigerant through various flow paths as explained hereinafter, and a set of valves to be described below which control the refrigerant flow through the various lines and which operate to reverse the direction of refrigerant flow to render the circuit reversible. The sludge handling network includes a raw sludge tank 13 located beneath the two heat exchangers for receiving raw sludge discharged by either of the exchangers, a melted sludge tank 14 which is similarly disposed beneath the heat exchangers for receiving melted sludge discharged by them, a pump 16 for circulating raw sludge from the raw sludge tank through either of the heat exchangers, a pump 18 for circulating melted sludge or cool water through either of the heat exchangers or for transferring the melted sludge out of the system, a raw sludge storage tank 20 which receives raw sludge admitted through a valve 88 and serves as a raw sludge reservoir for the system, a raw sludge thickener tank 22 in which raw sludge is allowed to settle to permit the decanting of some relatively clear water, and a pump 24 for transferring raw sludge through valve 113 into raw sludge tank 13. The various other elements, valves, lines and controls will be described hereinafter.

The general operation of the system illustrated in FIG. 1 is as follows. The flow of refrigerant from compressor 8 to either of the heat exchangers, the flow from either of the heat exchangers to the other heat exchanger or to the compressor, and communication between the heat exchangers and knockout pot 6, occurs in refrigerant flow lines which can be opened or closed by valves 26 through 31 to define the various refrigerant flow paths. Compressor discharge gas is-directed either through valve 27 or valve 30, while suction gas passes through either valve 26 or 29. Valves 28 and 31 are connected to the bottom of knockout pot 6 to equalize the refrigerant level in pot 6 with the level in the evaporator, as explained hereinaftenWhen heat exchanger 2 is serving as the condenser, valves 29, 30 and 31 are closed and valves 26, 27 and 28 are open. whereby refrigerant from the compressor is directed through valve 27 to the condensing heat exchanger 2, while low pressure refrigerant vapor is being discharged from evaporating heat exchanger 4 through valve 26 towards compressor 8. Condensed refrigerant flows from the condensing heat exchanger 2 to evaporating heat exchanger 4 through the line controlled by valve 32. Likewise, when the functions of the heat exchangers are reversed, the conditions of valves 26-31 reverse (but during part of the cycle, vaves 26-31 are open and refrigerant flows by virtue of a pressure differential without passing through the compressor). Valves 26-31 can be double action pneumatic valves which are controlled by solenoid valves, although other types of refrigerant valves could be used in their stead. The foregoing solenoid valves can be operated automatically by float switches 46, 48, 50 and 52 which operate in response to the level of sludge in their respective tanks. Valve 32 is advantageously a pneumatic valve controlled by a level controller 7 on knockout pot 6, which is set to maintain a liquid refrigerant level near the top of the evaporating heat exchanger. Refrigerant flow to valve 32 can be observed through a sightglass 33.

The purpose of the system is to freeze and subsequently thaw sludge to effect the separation of solid constituents in the sludge from their liquid vehicle. Accordingly, raw sludge is fed to the evaporating heat exchanger where it is placed in heat exchange relationship with evaporating refrigerant so that heat is transferred from the sludge to the refrigerant. In order to accomplish the foregoing, pump 16 delivers raw sludge from tank 13 through appropriate sludge lines to the evaporating heat exchanger. Raw sludge from pump 16 can follow alternate flow paths through the sludge lines controlled respectively by valves 34 or 35. When valve 34 is open and valve 35 is closed, raw sludge is directed to heat exchanger 4, whereas when valve 35 is open and valve 34 is closed, heat exchanger 2 receives the raw sludge. Valves 34 and 35, as well as valves 40, 41, 42 and 45, are advantageously operated by air pistons under the control of solenoid valves, which can in turn be automatically operated by float switches 46, 48, 50 and 52.

It is possible that all of the raw sludge fed to the evaporator will not freeze, and therefore it is desirable to recirculate the unfrozen raw sludge. For reasons which shall be explained below, it is also desirable to recirculate melted sludge discharged from the condensing heat exchanger. Hence, it is advantageous to direct raw sludge discharged by the evaporator to raw sludge tank 13, and to direct melted sludge discharged by the condenser to melted sludge tank 14. Accordingly, dampers or baffles 36 and 38, one associated with each heat exchanger, are pivotally mounted in the discharge paths of each of the heat exchangers, and are selectively displaceable for directing raw sludge to tank 13 and melted sludge to tank 14. When heat exchanger 2 is the condenser, and heat exchanger 4 is the evaporator, baffles 36 and 38 are positioned as shown by the solid lines. Dampers 36 and 38 are movable by damper operators 56 and 58, which can be electrically actuated air pistons. Damper operators 56 and 58 can be controlled by electrical timers which coordinate the operation of operators 56 and 58 with the operation of other components of the system.

The condenser should function to melt sludge previously frozen in that heat exchanger and to discharge that sludge for settling or subsequent treatment. Hot, pressurized refrigerant circulating through the condenser gives off heat to the frozen sludge, and causes the sludge to melt. In order to facilitate and expedite the melting of the frozen sludge, melted sludge can be pumped from tank 14 to the condensing heat exchanger by pump 18 (if an insufficient quantity of melted sludge is available, as during start up, cool water can be admitted to tank 14 through valve Depending on which of valves 40 and 41 are open (the other valve being closed) melted sludge from tank 14 is directed to one of the two heat exchangers. When heat exchanger 2 is the condenser, valve 40 is open and valve 41 is closed, whereas when heat exchanger 4 is the condenser, valve 41 is open and valve 40 is closed. The melted sludge flows down the condensing heat exchanger in direct contact with the sludge ice therein, and the combined transfer of heat from the condensing refrigerant and from the melted sludge to the frozen sludge causes the ice to melt. The damper at the base of condensing heat exchanger directs the melting sludge into melted sludge tank 14.

When the desired amount of sludge is frozen in the evaporating heat exchanger, pump 16 is shut down to conserve power and to prevent the needless circulation of raw sludge. Pump 18 is usually run after the shutting down of pump 16, because the ice in the condenser has been found to melt substantially sooner than a like amount of sludge freezes in the evaporator, so that the recirculating melted sludge absorbs heat from the condensing refrigerant. A cooler 59 can be provided in the a valve 61. Valve 42, which controls the flowthrough a sludge line leading from theoutput side of pump 18, can be opened at this time to direct a predetermined quantity of melted sludge from the system to a surge tank 44, from whence it can pass at a slow rate through a valve 112 to settling tanks (not shown) or to a subsequent processing station.

It has been found to be advantageous to subcool the sludge ice in the evaporating heat exchanger after pump 16 is shut down because greater separation of the sludge occurs, possibly due to an increased breakdown of the lattice structure of the sludge. Therefore, compressor 8 is run for a predetermined period after pump 16 shuts down. This is an appropriate time to open valve 42 for transferring a predetermined charge of raw sludge into tank 44.

Preparations are made to reverse the roles of the heat exchangers when sludge in the evaporator has frozen sufficiently and compressor 8 has stopped. Pump 18 is shut down justprior to the reversal of the system to prevent any melted sludge from being carried over into tank 13 when dampers 36 and 38 reverse their positions. At this time, the system is reversed. The conditions of the pairs of valves 34 and 35, and 40 and 41 are reversed to reverse the heat exchangers to which the raw and melted sludge flow. Dampers 36 and 38 are switched in accordance with the changing roles of heat exchangers 2 and 4. Compressor 8 is not running, and valves 26 through 31 are opened to permit the unimpeded circulation of refrigerant between heat exchangers 2 and 4 which occurs by virtue of the pressure differential in the refrigerant. Raw sludge pump 16 is re activated and raw sludge, now being pumped to the new evaporator, is cooled by evaporating refrigerant while the sludge ice in the new condenser begins to melt. When the pressure differential of the refrigerant becomes insufficient to drive the refrigerant through its operating circuit, compressor 8 is restarted. The appropriate valves 26-28 or 29-31 are closed, and the refrigerant proceeds through its normal cycle to freeze sludge in the new evaporator and to melt sludge in the new condenser.

Further details of the system, including the electrical and pneumatic control circuits, are setforth in previously cited Ser. No. 356,276.

As mentioned earlier, knockout pot 6 serves the dual functions of removing refrigerant liquid from the compressor gas stream to protect the compressor, and operates to maintain the level of liquid refrigerant in the heat exchanger serving as the evaporator at an optimal level. Referring to FIG. 2, knockout pot 6 may be seen to include a housing 120 defining a chamber 122 which is adapted to receive and contain liquid refrigerant in its lower portion. Knockout pot 6 is disposed at a height commensurate with that of the heights of the two heat exchangers, and the lower portion of knockout pot 6 which contains liquid refrigerant is in alternate communication with the liquid refrigerant in the heat exchangers through a refrigerant line 124 and the lines controlled by valves 28 and 31 (FIG. 1). Whichever of valves 28 and 31 controls flow through the line leading from the evaporator is opened, while the other valve is closed, so that the level of liquid refrigerant in knockout pot 6 is the same as the level of liquid refrigerant in the evaporator. This level is externally observable through a level gauge glass 5 which communicates with the refrigerant in knockout pot 6 through refrigerant lines controlled by valves 128 and 130. The heat transfer capacity of I .the evaporator can be optimized by maintaining as high a level as possible of liquid refrigerant therein. The amount of liquid refrigerant in the evaporator is controlled by valve 32 in the refrigerant line connecting the two heat exchangers. In the course of operation of the system, heat is transferred from sludge freezing in the heat exchanger serving as the evaporator to the refrigerant in that heat exchanger, and the refrigerant evaporates and flows towards conpressor 8. Liquid refrigerant from the condenser flows through the line controlled by valve 32 into the evaporator. By regulating the opening of valve 32, the level of liquid refrigerant in the evaporator is controlled.

The operation of valve 32 is effected by means of a level controlling device such as a displacer cage assembly of the type sold under the trademark LEVEL- TROL by the Fisher Controls Company of Marshalltown, Iowa. A level controlling device of the latter type is incorporated in knockout pot 6 and includes a displacer or float 132 which floats on liquid refrigerant in knockout pot 6, a rod 134 attached to and extending from displacer 132, and a torque tube 136 connected to rod 134 to rotate about its longitudinal axis in response to vertical movement of displacer 132 and rod 134. Such rotation can advantageously be achieved by having rod 134 be angularly displaced from the normal, extending from torque tube 136 to the ground, and by having torque tube 136 be keyed to the end 138 of rod 134. Thus, when the level of refrigerant in the lower portion of chamber 122 changes, the resulting displacement of displacer 132 causes torque tube 136 to rotate. A level control mechanism 140 which is responsive to the rotation of torque tube 136, operates to vary the air pressure on a pneumatic control device operatively connected to valve 32. Valve 32 can be any of a variety of pneumatically operated valves whose opening is variable depending on the amount of air pressure exerted thereon.

Refrigerant vapor enters knockout pot 6 through inlet 126 above the level of the liquid refrigerant in the pot. In order to isolate displacer 132 from fluctuations in the level of the liquid refrigerant in which it is floating which could result from turbulence caused by the incoming refrigerant, a baffle 142 is provided. Baffle 142 functions to keep displacer 132 and the liquid in which it is resting out of the incoming refrigerant stream whereby the liquid is rendered quiescent. The net result is that displacer 132 is only displaced when the level of the refrigerant liquid changes because the level of liquid in the evaporator has changed.

Since chamber 122 of knockout pot 6 defines a space above the liquid refrigerant, refrigerant vapors rise thereto. Any liquid entrained in these vapors separates out into the liquid below by virtue of its weight so that only gaseous refrigerant passes through the outlet 144 to suction line 146 leading to compressor 8.

The invention has been described in detail with particular reference to a preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

I claim:

\ 1. In a reversible refrigeration system including a pair of heat exchangers serving alternate and opposite functions as flooded evaporators and as condensers, and a compressor connected in a refrigeration circuit by lines defining refrigerant flow paths, the invention comprismg:

valve means in the line leading from the condenser to the evaporator for regulating the rate of flow of refrigerant from the condenser entering the evaporator; and apparatus in the refrigerant flow path between the evaporator and the compressor for operating said valve means and for separating liquid from the refrigerant vapor flowing to the compressor, said apparatus including: means defining a chamber for holding a quantity of refrigerant liquid in the lower portion of the chamber at a level equal to the level of refrigerant liquid in the evaporator, and for holding refrigerant vapor above the refrigerant liquid whereby liquid entrained in the vapor separates out into said quantity of liquid; a refrigerant vapor inlet to said chamber; refrigerant lines connecting said chamber to each of the heat exchangers, and means for closing the line to said chamber from the heat exchanger functioning as the condenser, for maintaining the refrigerant liquid in said chamber in communication with the refrigerant liquid in the evaporator and for transferring refrigerant vapor from the evaporator to said inlet, whereby the levels of refrigerant liquid in the evaporator and in said chamber are equal; means responsive to changes in the level of liquid refrigerant in said chamber for controlling the operation of said valve means to maintain the refrigerant liquid in the evaporator at a predetermined level; and an outlet from said chamber to the compressor,

said outlet being disposed above said lower portion for discharging refrigerant vapor to the compressor. 2. The invention according to claim 1 wherein said means for controlling the operation of said valve means comprises a float in the refrigerant liquid in said chamher, said float rising and falling with corresponding changes in the level of the refrigerant liquid to effect control of said valve means.

3. In a refrigeration system including a flooded evappaths, the improvement comprising:

valve means in the line leading from the condenser to the evaporator for regulating the rate of flow of refrigerant from the condenser entering the evaporator; and

apparatus in the refrigerant flow path between the evaporator and the compressor for operating said valve means and for separating liquid from the refrigerant vapor flowing to the compressor, said apparatus including:

means defining a chamber for holding a quantity of refrigerant liquid in the lower portion of the chamber at a level equal to the level of refrigerant liquid in the evaporator, and for holding refrigerant vapor above the refrigerant liquid whereby liquid entrained in the vapor separates out into said quantity of liquid;

a refrigerant vapor inlet to said chamber;

conduit means for maintaining the refrigerant liquid in said chamber in communication with the refrigerant liquid in the evaporator and for transferring refrigerant vapor from the evaporator to said inlet, whereby the levels of refrigerant liquid in the evaporator and in said chamber are equal;

a float rising and falling with corresponding changes in the level of liquid refrigerant in said chamber for controlling the operation of said valve means to maintain the refrigerant liquid in the evaporator at a predetermined level;

baffle means disposed in the refrigerant liquid in said chamber between said inlet and the site of said float, for reducing turbulence in the refrigerant liquid near said float; and

an outlet from said chamber to the compressor,

said outlet being disposed above said lower portion for discharging refrigerant vapor to the com- PI'CSSOI'. 

1. In a reversible refrigeration system including a pair of heat exchangers serving alternate and opposite functions as flooded evaporators and as condensers, and a compressor connected in a refrigeration circuit by lines defining refrigerant flow paths, the invention comprising: valve means in the line leading from the condenser to the evaporator for regulating the rate of flow of refrigerant from the condenser entering the evaporator; and apparatus in the refrigerant flow path between the evaporator and the compressor for operating said valve means and for separating liquid from the refrigerant vapor flowing to the compressor, said apparatus including: means defining a chamber for holding a quantity of refrigerant liquid in the lower portion of the chamber at a level equal to the level of refrigerant liquid in the evaporator, and for holding refrigerant vapor above the refrigerant liquid whereby liquid entrained in the vapor separates out into said quantity of liquid; a refrigerant vapor inlet to said chamber; refrigerant lines connecting said chamber to each of the heat exchangers, and means for closing the line to said chamber from the heat exchanger functioning as the condenser, for maintaining the refrigerant liquid in said chamber in communication with the refrigerant liquid in the evaporator and for transferring refrigerant vapor from the evaporator to said inlet, whereby the levels of refrigerant liquid in the evaporator and in said chamber are equal; means responsive to changes in the level of liquid refrigerant in said chamber for controlling the operation of said valve means to maintain the refrigerant liquid in the evaporator at a predetermined level; and an outlet from said chamber to the compressor, said outlet being disposed above said lower portion for discharging refrigerant vapor to the compressor.
 2. The invention according to claim 1 wherein said means for controlling the operation of said valve means comprises a float in the refrigerant liquid in said chamber, said float rising and falling with corresponding changes in the level of the refrigerant liquid to effect control of said valve means.
 3. In a refrigeration system including a flooded evaporator, a condenser and a compressor connected in a refrigeration circuit by lines defining refrigerant flow paths, the improvement comprising: valve means in the line leading from the condenser to the evaporator for regulating the rate of flow of refrigerant from the condenser entering the evaporator; and apparatus in the refrigerant flow path between the evaporator and the compressor for operating said valve means and for separating liquid from the refrigerant vapor flowing to the compressor, said apparatus including: means defining a chamber for holding a quantity of refrigerant liquid in the lower portion of the chamber at a level equal to the level of refrigerant liquid in the evaporator, and for holding refrigerant vapor above the refrigerant liquid whereby liquid entrained in the vapor separates out into said quantity of liquid; a refrigerant vapor inlet to said chamber; conduit means for maintaining the refrigerant liquid in said chamber in communication with the refrigerant liquid in the evaporator and for transferring refrigerant vapor from the evaporator to said inlet, whereby the levels of refrigerant liquid in the evaporator and in said chamber are equal; a float rising and falling with corresponding changes in the level of liquid refrigerant in said chamber for controlling the operation of said valve means to maintain the refrigerant liquid in the evaporator at a predetermined level; baffle means disposed in the refrigerant liquid in said chamber between said inlet and the site of said float, for reducing turbulence in the refrigerant liquid near said float; and an outlet from said chamber to the compressor, said outlet being disposed above said lower portion for discharging refrigerant vapor to the compressor. 